Field of the Invention
The present invention relates to a method and an apparatus of transceiving a signal using a link adaptation in a communication system.
Description of the Related Art
A next generation communication system has been developed to the form of a mobile communication system for providing services capable of transceiving high speed large capacity data to a mobile station (hereinafter referred to as ‘MS’).
The most basic problem of the next generation communication system is how efficiently and reliably data can be transmitted through a channel. Accordingly, it is essential to increase efficiency of a system using transmission power suitable in a system channel environment or a Modulation and Coding Scheme (hereinafter referred to as ‘MCS’). An efficient communication link may be collectively operated without consuming a system resource by suitably controlling transmission power of a transmission channel.
To apply such a link adaptation, a base station (BS) must estimate link quality of a data transmission channel. In this case, the BS includes various types such as Femto cell, Pico cell, Relay node as well as a general base station. Accordingly, in a case of downlink, the MS measures link quality of a signal received from the BS, and reports the measured link quality of the received signal to the BS.
Meanwhile, a wireless resource for transmitting data is divided into a plurality of regions, and a method of transmitting data of different applications or the same application but different types is applied to each region. In this case, when transmitting data to each region, each region may apply different transmission power or MCS levels. An LTE downlink is described as one embodiment. One subframe is divided into a PDCCH transmission region for transmitting scheduling relation information and other control information and a PDSCH region for transmitting general data. The BS may change transmission power and an MCS used for transmitting PDCCH data and PDSCH data. Control information transmitted to the MS is transmitted to the PDCCH region, and user data are transmitted to the PDSCH region.
An MS in a current communication system reports a Channel quality indicator (CQI) representing link quality with respect to entire or specific resource regions to the BS. The BS determines transmission power of each resource region and an MCS based on this. Data to be transmitted to each region or robust or loose transmission power according to a transmission scheme are applied to the MCS.
However, link quality of respective regions may be different from each other. This may occur due to very many reasons, and a representative reason is as follows. FIG. 1 is a diagram illustrating interference (PDCCH vs PDSCH) by regions in a communication system according to the related art.
First, a case where interference amounts are different for each region is described. For example, it is assumed that transmission timing of BSs is synchronous, and the transmission resource is a system obtained by time-multiplexing a resource for transmitting control information in one subframe and a resource for transmitting data information. In this case, when an MIMO mode transmitted to each region is different, statistics of interference received by each region are different from each other, so link quality is changed. Second, a case where loading is different for each regions will be described. As shown in FIG. 1, when a frequency use loading of a PDSCH region is different from a frequency use loading of a PDCCH, interference statistics are different for each region. Third, there is a case where different transmit powers are applied for each region. Fourth, there is a case where different fadings occur for each region.
Accordingly, an exact link adaptation cannot be applied by only link quality CQI information with respect to total or specific resource regions in the same as in a current communication scheme. Due to this, data reception of each region is not easily achieved or transmission power or resource is inefficiently operated. In particular, when transmission power of control information or an MCS associated with scheduling is wrongly selected, because resource allocation information for transceiving data cannot be received, transmission efficiency is significantly deteriorated and an abnormal operation is induced so that communication become impossible.
An LTE system according to the related art is designed on the assumption that a channel state of a control information region (PDCCH region) is the same as a channel state of a data channel region (PDSCH region) (signal-to noise ratio received when transmitting the same power). Accordingly, regardless of a performance of each region, a channel state in one subframe is measured and the measured channel state is transmitted to a base station with CQI. Accordingly, a CQI in the LTE system according to the related art indicates an average channel state without discriminating the region. In this case, a channel transmitting the CQI uses the PUCCH. Such CQI report is periodically transmitted in a preset time.
A base station (BS) having received the information determines an amount, an MCS, and transmission power of a data channel (PDSCH) to be transmitted to a downlink based on the CQI. The BS is used to determine the MCS and transmission power of data to be transmitted to the PDCCH being control information. However, as described above, if a channel state of the data transmission region is different from a channel state of the control information transmission region, there may be a problem that MCS levels and transmission power of two channels must be determined by one measured value.